Peach-firming dip tested

University of Georgia researchers have developed a solution that could help prolong the shelf life of fresh peaches.

Peach growers have to pick peaches earlier than ideal so they don't perish en route from the orchards to retail stores.

“Growers pick peaches when they reach what's called the 'market mature' stage,” says Stan Prussia, an engineer in the biological and agricultural engineering department with the UGA College of Agricultural and Environmental Sciences.

“They have to be sure their product can survive shipping,” he says, “because when a shipment reaches its destination, a sample is pulled and if the peaches are too soft, the whole load can be rejected.”

Working with visiting scientist Grzegorz Lysiak of the Agricultural University in Poznan, Poland, Prussia and UGA agricultural economist Wojciech Florkowski applied a method currently used on apples.

“We dipped half a batch of peaches in a 1-percent calcium chloride solution for half an hour. The other half we left untouched,” Prussia says.

He says the solution is similar to what is used for adding chlorine to swimming pools. “Table salt is sodium chloride, and this is calcium chloride,” he says.

The test peaches were then put through storage and shipping conditions.

“Peaches normally don't stay in storage for more than two weeks. But we kept our test peaches in storage longer,” Prussia says. “After 21 days of storage, we saw a definite difference as the treated peaches remained firmer.”

Adding the salt solution wouldn't be hard for growers. They normally have hydrocoolers in their packing houses to cool the peaches with water, Prussia says.

“However, we would need to make sure the salt solution does not harm the hydrocooling equipment over time,” he says.

Another glitch the researchers are working out is the slight aftertaste the solution leaves behind. Using a taste panel, the scientists found that it “slightly changes” the taste of the peaches.

“It was a slight change,” Prussia says. “But it was enough of a change that our taste panel detected it.” The research team is now working to modify the salt solution.

“We have to do more research to see if we can lower the concentration of the solution so the taste isn't affected and (growers) still get the benefits,” he says.

The scientists are also looking into an alternative to dipping the peaches in the packing houses.

“We'd like to try spraying the peach trees while they're growing, either once a week or once every two weeks,” Prussia says. “This way, the calcium would get into the peaches as they grow.”

He says this method is used now on other crops with no aftertaste effects.

A postharvest specialist, Prussia says peaches could be allowed to ripen longer on the trees if they weren't too soft to ship. Staying longer on the trees would make peaches sweeter.

Prussia hopes spraying the salt solution onto the peach trees will be the answer to this dilemma.

“It would be great if the peaches could be left on the trees longer to develop full flavor, still ship well and arrive tasting better for consumers,” he says.

The researchers are now sharing their findings with the Georgia Agricultural Commission for Peaches, which partially funded the first stage of the project.